How Long Does It Take for a Mass to Freeze or Melt?

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The discussion addresses the time required for a mass to freeze or melt, emphasizing that the equation Q = mcΔt is not applicable during phase changes, as Δt equals zero at the freezing/melting point. Instead, the heat of fusion (Q = mΔHfus) must be considered to quantify the energy needed for phase transitions. The freezing time for a substance, such as water, is influenced by various factors including the temperature of the cooling environment, the placement of the cooling source, and the thermal conductivities of both water and ice. Overall, the time it takes for a mass to freeze or melt is complex and dependent on multiple variables. Understanding these factors is crucial for accurate predictions in thermal dynamics.
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Hello.

We all know ##Q = mc\delta t##, but is there an equation which describes the time it takes for a mass to freeze/melt given a certain specific heat capacity? This way you could for example quantify how long it takes room temperature to freeze in a freezer (or any element).
 
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Mayhem said:
how long it takes room temperature to freeze

If by 'freezing' you mean 'change from liquid phase to solid phase', then room temperature does not freeze.

The ##\ Q = \dot m\,c_p\,\Delta t\ ## equation doesn't fly (for a pure substance ##\ \Delta t= 0\ ## , i.e. the phase change takes place at the freezing/melting point) .

Instead, a material-dependent heat of melting has to be removed (c.q. supplied for melting), so at best you have ##\ Q = \dot m\,\Delta H_{fus}\ ##.

How fast it goes depends on a whole lot of factors.

##\ ##
 
BvU said:
The ##\ Q = \dot m\,c_p\,\Delta t\ ## equation doesn't fly (for a pure substance ##\ \Delta t= 0\ ## , i.e. the phase change takes place at the freezing/melting point) .
I think t is time here.
@Mayhem, having got, say, a tank of water to 0C, the time it takes to freeze it all depends on the applied cooler temperature, where it is applied, the conductivities of water and ice, and the convection within the tank.
 
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